will have a higher softening point than that of the product blown a t higher temperatures. I n the present experiments, the asphalt flux was heated initially to 1IOo C., to fluidize the material completely, before any gas was added. T h e gases were added a t a rate of 1.25 cc. per minute-gram (40 c u . feet per minute-ton). T h e temperatures \vere gradually increased to 158@C . in order to maintain fluidity as the reaction proceeded. Hokvever. it may be observed from Table I\’ that even with the lower reaction temperatures used in these experiments, Lvhich undoubtedly increased blowing time, and \vith the relatively low gas rate used, asphalts of a coating-grade roofing quality were prepared. T h e asphalts made a t the lower temperatures had higher penetrations than commercial asphalts of similar softening points, which confirms the findings of Chelton, Traxler, and Romberg ( 7 ) . T h e penetration index values \\.ere higher than those of the commercial products and were typical of most blown asphaltic bitumens whose penetration index values generally range from +2 to + S (23). literature Cited (1) Abraham, H., “Asphalts and Allied Substances,” 6th ed., Vol. 11. D. 166. Van Nostrand. New York. 1961. (2) Zbtd., pp. 168-70. (3) Asphalt Ins:. Quart., July 1962. (4) Bamford, C. H.. Jenkins, A. D., Johnston, R., Trans. Faraday SOC.5 8 , 1212 (1962). (5) $ampbell, P. G., \$’right, J. R., J . Res. .Vatl. B u r . Std. 68‘2, 113 (1964). (6) Campbell, P. G., Liright, J . R., Bowman. P. B., M a t e r . Res. Std. 2 , 988 (1962). ( 7 ) Chelton. H. M., Traxler, R. N., Romberg, J. LV., Ind. Eng. Chem. 51, 1353 (1959).
(8) Culmer, H. H., U. S.Patent 1,430,538 (Oct. 3>1922). (9) de Gerbeth, F. I>.,Ibid., 81,071 (.lug.18, 1868). (10) Evans, Ivf. G., Uri; N., .Vature 164, 404 (1949). (11) Fischer, E. J., ? P e r u . Bitumen 33, 251 (1935). 112) Giinnel. F.. Bitumen. Tewe. dsbhaite. Peche 9. 308 11958) (13j Graham. \i-.. Cudmore. \V, ‘J. G.. Heyding. R.’ D.: ’Can. J. Technol. 30, 143 (1952). (14) Greenfeld, S.H.: ISD. ENG. CHEM.,PROD.RES.D E V E I O P3,. 1’58 (1964). (15) Hammond. G. S., Mahoney, L. R . ? Nandi, U. S.,J . Am. Chem. Soc. 85, 737 (1963). (16) IHoiberg. A. ,I., Proc. Assoc. Asphait Palling Technologists 19,
225 (1950). (17) Knowles. E. C.. McCoy. F. C.. \Veetman, B., Eckert, G. LV., Division of Petroleum Chemistry (XCS) , Symposium o n Chemistry and Composition of .\sphalts, p. A29. April 1958. (18) Kovacic. P., Morne\veck. S.T.. Volz, H. C.. J . Orq. Chem. 28, 2551 (1963). (19) Kovacic, P.: Vob. H. C., J . dm. C‘hem. Soc. 81, 3261 (1959). 120) \ , Kovacic. P.. \Vu, C.. J.Poivmer Sci.47. 45 11960). (21) Leightoi;. P. .A,, ’.Photochemistry of .A& Poilution.” .\cademic Press, New York, 1961. (22) Okamura, S..Higashimura. T.. Sakurada, Y..Roqyo Raqaku Zasshi 61, 1640 (1958); C.A. 55, 27951 (1961). 123) Pfeiffer. .J. Ph.. “ProDrrties of Asphaltic Bitumcn.” pp. .. 12, ’ 1’66-70. tlsevier, . Its Composition, Properties and Uses.“ pp. 127-8, Reinhold, S e w York, 1961 (26) Liright, .I. R., Campbell, P. G.. J . z 4 ~ p lChrm. . (London) 12, 256 (1962). (27) Zechemayr, O., Ger. Patent Appl. G 2254 (Nov. 13, 1952). RECEIVED for reiiew March 30. 1964 . \ C C E P T E D June 15, 1364 Di\ ision of Petroleum Chemistry, 147th Meeting. ACS, Philadelphia, Pa., April 1964.
A NEW RUBBER DERIVED FROM
PROPYLENE OXIDE E. E. G R U B E R , D. A.
MEYER, G . H. SWART, AND
K . V. WEINSTOCK
Resrarch 3 Dedopment Center, The General Tire & Rubber Co., Akron. Ohio
A sulfur-curable elastomer with an unusual combination of properties was prepared from propylene oxide and an unsaturated epoxide. Since the raw polymer was essentially amorphous, the gum tensile strength was low, but with ISAF carbon black reinforcement tensile strengths of 2500 to 3000 p.s.i. were possible. This rubber showed remarkable resistance to fatigue under dynamic conditions where high temperatures were developed. Exceptional low-temperature flexibility, excellent ozone resistance, and moderate oil resistance were observed. Rebound and heat build-up were comparable to natural rubber. Modulus i s essentially constant from room temperature to -30” F. Heat resistance studies indicated that this rubber i s substantially better than natural rubber. This new and uniquely different polymer should b e of interest as a specialty rubber in many automotive and mechanical goods applications.
A
elastomeric copolymer of propylene oxide and an unsaturated epoxide (POR) has been developed. This rubber is sulfur-curing and has a combination of properties that indicates utility as a specialtv rubber of particular interest to the mechanical rubber goods industry for automotive and industrial applications This paper describes the properties of a specific copolymer of propvlene oxide and an unsaturated epoxide. called D) nagen XP-I 39. \vhich is being produced in developmental quantities. 194
EM'
I&EC
PRODUCT RESEARCH A N D DEVELOPMENT
Polymerization and Structure
Techniques for the polymerization of propylene oxide to polymers of low molecular lveight have been known for many years, and these polymers are \videly used today in the m a n u facture of urethane foam. T h e polymers used in’this industry are? ho\vever: functionally terminated polymers of lo\\. molecular \ceight that require coupling with di- or polyisocyanates to produce usrful materials of high molecular weight. Only in recent years has the propylene oxide been directly poly-
Polymerization of Propylene Oxide to High Molecular Weight
Table 1.
CHi
'"' .\ = --OM---. --OK. -011. -C1, -K. or ----H bi = metal atom or metal atom bonded to oxygen K = alkyl or ary-1 RqirrPncr
Cn/~llJsf
+ C:.illsO SrC!O, t I H P O %1iC1?+ ~iso-PrO)i.-\l ZnR? + I H s O :\IR;, + 1 1 2 0 + acetylacetorie FeCli
Table II.
Pruitt and Baqqett Bailey Price Fur ~ikawa Herculrs Powder CO.
[
70) (7)
(8) 3) (:i)
Copolyrnerizable Unsaturated Epoxides Mentioned in Issued Patents
0
/ \
Butadiene monoxide
HyC-CH--Cl-T--
CHn
0
'\
X l l y l glycidyl ether
I-I~C-CII-CH~--O--CI~a~-Cl-I- -.C€lj
0
0
l~
/ \
Glycidyl acrylate
CH,= CH-C-O-CHy-CH-CH1
Vinyl cyclohexene monoxide
H2C= C H - A
CH3 2-hkthyl-5.6-epoxy1-hexene
0
/ \
HnC = C-CHy-CH2-CH-CH2
merized to high molecular weight rubbers. as revielved by Hendrickson ( J ) and Bawn and Ledwith ( 2 ) . Recently some of the properticss of a rubber from propylene oxide have been described by Xladge ( 6 ) and Hendrickson! Gurgiolo, and Prescot1 (-1). Table I shotvs the general form for the polymerization of propylene oxide using a coordination catalyst and lists some of the catalysts that have been reported. These catalysts d o not all give the same rubbery products. Some of the polymerization products are highly crystalline. some are amorphous. and others are mixtures of these tic0 forms. Crystalline polypropylenr oxide is isotactic in structure and the amorphous phase is atactic as clrwribed by Price and Osgan ( 9 ) and by S a t t a (7). T h e polymerization is generally carried out in a solvent in a manner similar to that used for other solution stereopolymers. Early w o r k m reasoned that a propylene oxide r u b b r r should have interesting properties because free rotation that occurs about an oxygen-carbon bond \could produce a highly flrxiblr po1ymc.r chain Lcith good low temperature properties and good dynamic response, and the oxygen atom would contribute the polarity to provide some oil resistancr. T o produce a rubber that will vulcanize rvith conventional sulfur a n d accderator systems, some unsaturated groups must be incorporated along the polymer chain. Table I1 lists some of the unsaturdted epoxides that have been reported for this type of rubber. Incorporation of any one of these monomers into the propylene oxide polymer will place the unsaturation in a side chain. This is believed to contribute better resistance to thermal and oxidative degradation than when the unsaturation is in the main chain. T h e catalyst a n d unsaturated comonomer used in the P O R discussed in this paper a r e similar to those described above but are not specifically described ar this time. R a w Polymer Properties and Processing
Table Ill.
Typical Properties of R a w Polymer
White to light amber Baled c r u g b 1.02 60 + 10 ML-4 at 21 2 F. Essentially amorphous (x-ray) Broad Nonstaining and nondiscoloring
Cnlnr __~..
Physical form Specific gravity Mooney viscosity Crystallinity .Molecular weight distribution Antioxidant
T h e propykne oxide rubber as produced is described in Table 111. T h e rubber will band readily on the mill after a short breakdoum a n d shows excellent processibility even in lightly loaded compounds. Best milling and calendering behavior occurs v i t h rolls a t a temperature in the range of 140' to 2003 F. T h e roll temperature is not critical in this range or even a t higher temperatures. There is some tendency to adhere to cold rolls. Vulcanization and Physical Properties
Table IV.
Typical Formulations and Properties
Forniulation . ' l c c d m t o r ' ' Si1l.fur C u r e time at 300" F.:
min. 300"; h l . p.s.i. Tensile. D . s . i .
A TAM7'.C1 0.6
B CBS 7.4
C 7 M T D 7.0
0.8
1.5 ___
0.6 ~
30 60 30 60 30 60 1125 1350 1185 1635 1175 1340 2750 2715 2800 2650 2615 2425 6'0 560 660 490 590 520 60 64 61 63 62 65 48 5 465 465
I longation shale \ I e a i . pi C otnp 5rt Zlethod B, 22 ill at 212" r 52 30 G7 46 41 30 hloonry scurch. min. at 2-( 3c. F . I' 13 9 Forniulation. POR 100.0, ISAF black 45.0. stearic acid 1 .0: z i n c uxitle 3.0. KBC: antioxidant 1.O. sulfur and accelerator as itidicarrd. " 7'.11 7-.\f. 7'Pirnniethyl thiurarn hrii:othia:oir siiljrnoniidP. T~\fT U .
CBS. CyclohrxylTrtramrthyl thiurnrn disiiiS;de. monosulfide.
Typical vulcanization systems and vulcanizate properties are shoicn in Table IV, T h e formulations shown here are representative of those generally found useful to date. There are. hoivever: many other possibilities that may be useful for special situations, just as there are n i t h the diene rubbers. T h e ingredients and their concentrations are similar to those commonly used in other rubbers. Zinc oxide and stearic acid are not essential to the production of good vulcanizates but are suggested for general use because of a slight leveling efTect on the cure and a minor effect on the processing behavior. Nickel dibutyl dithiocarbamate ( S B C ) is a n exceptionally good stabilizer for this rubber in dark-colored compounds. T h e phenolic antioxidants are also effective and can be used alone or in combinarion xcith S B C . Excellent \\,hire or pastel-colored compounds can be made lvith phenolic antioxidants. T h e general-purpose amine antioxidants and antiozonants are not recommended for propylene oxide rubber because they detract from its ozone resistance. T h e tensile properties are in a respectable range that is perhaps not as high as some of the VOL. 3
NO. 3
SEPTEMBER
1964
195
A
+FUMED
SILICA
FEF BLACK
/
I
,
-
/
/
LSRF BLACK
/ 10
-60 -40 -20
oi
Figure 1 .
4b
$0 FILLER LOADING, PHR
3'0
50
fo
80
Figure 2.
Tensile strength vs. filler loading
Response to Fillers
Since propylene oxide rubber is essentially a n amorphous rubber, it requires a reinforcing filler in order to develop good tensile a n d tear strength. T h e effect of a variety of loadings and types of fillers is shown in Figure 1 and Table L7. Formulation X from Table IV \\-as used lvith the appropriate level and type of filler. T h e response to blacks of different particle
Table V.
Filler Type
IS.4F black
FEF black
SRF black
Fumed silica ( Cab-0-Si1 M-5)
Hydrated silica (Hi-Si1 233)
40
80
Modulus at low temperatures
sizes is similar to that of other amorphous elastomers. in that there is a progressive increase in tensile strength as the particle size of the black decreases. LVith ISAF black. the t m d e strength reaches the range of 2500 to 3000 p " i , A pigmrnt of large particle size such as SRF black produces a compound with very high resilience but. of course. lo\\-er tensile strength. T h e gum tensile strength of this rubber is in the range of 400 to 600 p.s.i., as expected for a n essentially amorphous rubber. T h e behavior of the POR to\vard fine particle siiica filirrs is markedly different than lvith black fillers. Both fumed and hydrated silica pigments develop much higher tensile strengths
Propertiesa of POR with Various Fillers
300Yc .M. P.S.I.
Tensile, P.S.I.
Elong..
5
.Chore A
Tearh
Rebound.
I T d at
PZ
5
212" F.
10 20 30 40 50 60 70
300 500 750 1125 1475 1725 1425
525 1425 1925 2450 2650 2525 2450
450 580 570 560 540 480 420
36 42 50 56 64 70 76
55 105 270 480 520 495 380
84 79 73 67 60 54 49
15 23 35 4S.
30 40 50 60 70 80 90
1350 1675
1525 1850
520 490 430
46 54 60
85 125 190
81 76 71
40 50 60 70 80 90 100
650 750 950 1100 1250
66
60 55 50
, . .
1150 1125 1125 1200 1350 1400 1450
510 440 350 350 340 290 290
48 53 57 59 63 66 70
120 190 170 165 165
10 20 30 40 50
200 300 375 525 550
21'5 3800 3825 31 50 2425
950 050 070 030 990
38 46 55 62 71
40 125 355 440 505
84 76 68
10 20
225 350 500 600 725
1050 2100 2300 2450 2475
770 870 800 860 850
33 46 57 63 70
30 80 190 345 335
30 ..
60
OF.
Leuel: Ph.
40 50
75 95
83 82 80 -7 72 -0
65
9
59
71 16 23 33 46 54 -6 90 121 232 42 50 52
Cwnpnund~ .If o o nu?
53 62 70 75 86 104 113 60 65 76
88 1112
108 125
59 00 65 71
81 90
98
--
8 13
52
22
-4
60
37
53
37
101 1 60
86 85 79 '2 62
6 10 18 23 38
52 69 81 95 120
3
Tensileproprties determined on cure 30 min. at 300" F., rebound and heat build-up on cure 60 min. at 300" F . b Crescent t f a r . :lST.21 D 623. d2e U . Goodyear Healey. d Goodrichj7exometrr, t m p e r a t u r e rise at 212" F., 125p.s.i.. 0.775 inch stroke. e Compound .lfoonfy. .ZIL--l at 212" I;. (1
c
20
TEMPERATURE
9'0 Id0
general purpose rubbers. but higher than many of the specialty rubbers. T h e tear strength is excellent and other properties such as set and scorch are adequate for most applications.
0
196
I&EC PRODUCT RESEARCH A N D DEVELOPMEN1
Table VI.
Compounds Used in Comparative Tests"
POR
Polymer ISAF black ZnO Stearic acid NBC PBNA Sulfur TAMTAM CBS MBT
w-
oz
3
5 w n-
P
. . .
0.8 0.6
EP T 100 0 45 0 3 0 1 .Cl
'VR 100 0 45 0 3 0 1 0
SBR 100 0 45 0 3 0 1. 0 ... 1. 0 1.8
100 0 45 0 3 0 I .0 1 0
..
..
. .
1.o 1 . 5' 1 5'
1.0 2.5 ...
i 12
CR 100 0 36 5 5 0 1.0 1 0 . .
0.5 0 5,
4 0 Na-22 0 25 SBR. SBR 1500. LYR. 'VO. 7 smoked sheet. E P T . 'Vordei 7040. CR. Senprene U'R T . PB.VA. Phmyl-,?-naphthylamine. M B T . ,Llercaplohenrothiarole. ,Va-22. 2-1Mercaptoinidaroiine MgO
r 0
L
20
Figure 3.
60 RETRACTION, %
40
80
100
Temperature retraction curves
ASTM D1329, 2 5 0 '
Table VII.
elongation
a t low pigment loadings \\hen compared to ISAF black. T h e propylene oxide rubber develops unusually high tensile strengthb (over 3500 p s i . ) .i\ith 20 to 30 p.h.r. of a fumed silica such as Cab-0-Si1 M-5. T h e data in Figure 1 are plotted with respect to parts by Tveight. If parts by volume were used, the curve5 for the silica and black filler Lvould be someLvhat further separated.
Low Temperature Properties T h e lo\v temperature flexibility of propylene oxide rubber is substantially better than that of most common elastomers except for certain types of polybutadiene a n d silicone rubbers. Figure 2 sho\vs the change in 507, modulus Lvith temperature for propylene oxide rubber and several common elastomers. T h e term joyc modulus here is used in the sense commonly employed in the rubber industry and simply refers to the force required to extend the rubber tensile specimen by 50%. These dara Lvere obtained on a n Instron tester using a n extension rate of 2 inches per minute on a 2-inch gage length. Some portion of the stiffness shokvn by the chloroprene and natural rubber curves in Figure 2 m a y be due to crystallinity; ho\vever, this is believed to be a t a minimum because of the nature of the test and because of the smooth and regular manner in lvhich the modulus changes with temperature. T h e modulus of the propylene oxide rubber is almost constant over the range from room temperature d0Li-n to - 30' F. T h e temperature retraction curves for some of these same elastomers are sholvn in Figure 3. T h e d a t a here also indicate the good lo\\. temperature performance of the propylene oxide rubber. T h e slope of the curve for natural rubber clearly shows its tendency to crystallize, a n d conversely the slope of the curve for the propylene oxide rubber shoLvs essentially n o tendency to crystallize. T h e brittle point for the propylene oxide rubber by A S T M Procedure D 746 is about -80" F . T h e d a t a presented on low temperature properties kvere obtained on the compounds shown in Table 1'1 using a cure time and temperature appropriate to the type of elastomer. T h e black level was +educed in the polyhloroprene to bring it to the same volume loading as the propylene oxide rubber. T h e tensile and tear properties a t 75' and 212' F. for these compounds are sho\vn in Table V I I .
Tensile and Tear Properties
POR
SBR
30 300
30 300
JYR 30 287
EP7' yo ~. 320
CR 30 300
1225 2675 580 62 350
1675 4100 560 67 170
1800 4150 530 64 500
1450 2800 430 70 110
2000 2800 390 68 21 5
Properties at 21 2 F. 300% M; p.s.i. 1350 Tensile, p.s.i. 1500 330 Elong., ,7c Tear, pi 215
1700 2100 360 295
1260 3100 620 275
14.10 14.50 310 65
1290 1290 300 110
Cure time. min. Cure temp., F. Properties at 75 ' F. 300C;, .M, p.s.i. Tensile. p.s.i.
Elong., Shore .A
%
Tear, pi
~~
~~
O
Table VIII.
Rebound," % 32" F. 75' F. 212OF. Heat build-up,b F. 90" F. 212" F. a Goodyear Heaiqv.
Rebound and Heat Build-Up
POR
'YR
SBR
55 64 76
52 68 77
45 55 65
56 47 81 37 39 59 Goodrich Flexometer.
EPT
CR
4 51 6(1 68
34 54 64
102 75
83 58
Dynamic Properties
T h e rebound and heat build-up properties of the propylene oxide rubber are compared in Table VI11 with various other rubbers using the formulations of Table V I . These d a t a shoiv the rebound of the propylenr oxide rubber to be in the same range as natural rubber and some\vhat better than the SBR and other rubbers. T h e hcat build-up as measured on the Goodrich flexometer also approaches that of natural rubber a n d is better than SBR. Certain types of rubber parts such as motor mounts: vibration isolators, and drive couplings have servi'ce limitations that are dependent upon the ability of the rubber compound to support a load while subjected to cyclic defcrrmations and to high temperatures that are either internally or externally generated. In this type of service both the brat generation characteristic and ability to withstand high temperatures are important considerations in the rubber compound. T h e result of a comparison of propylene oxide rubber and natural rubber on a laboratory fatigue test designed to simulate such service conditions is shoum in Figure 4. I n this fatigue test a standard pellet of rubber is placed in a Goodrich flcxomrtcr a t VOL. 3
NO. 3
SEPTEMBER
1964
197
Ly
250' F. with a 0.175-inch stroke and 125-p.s.i. load, and a t 22minute intervals the temperature in the chamber around the specimen is raised 20' F. T h e change in dynamic height is continuously recorded. Failure is arbitrarily defined as the point lvhere a 0.250-inch change in height occurs. This is generally near the point a t which the sample ivould rupture. These data show a manyfold superiority for the propylene oxide rubber. This type of performance has been confirmed in accelerated testing of automotive motor mounts and other end items.
i 3 Z U
I U Y v,
I U
z I
I'
c3 Y
I
Z
FLEXING TIME -MINUTES
zi
Heat Resistance
49OoF,
410°F.
330°F,
250°F.
Figure 4. Fatigue resistance of propylene oxide rubber and natural rubber
Table IX.
Aged at 250 F 1300r, M. p s 1 Tensile D s i Elong, (tl Shore A
Heat Resistance of POR
0
50
700
1300 2550 550
2100 2390 335
2160
62
70
Hours
300
2100 2000 270 72
305 70
Aged at 300' F 300r, M, p s i 1300 Tensile. p s i 2500 1500 1250 Elo11g.. ':; 550 280 220 Shore -4 62 73 74 Formulation. POR 100.0, ISAF black 45.0. stearic acid 1.0. Z n O 3.0. NBC 1.0, T h I T M 0.6. sulfur 0.8. Table X.
Accelerated Ozone Tests
Bent loop specimens.
Elastomer
POR CR S B R (ISL;)" IIR" NK E PT Paracril A J . Butyl 275. Table XI.
Time to flrst cracks
Hours, at 50 P.P.H..M. Otoni >3000
.Wznutes, ad 7yc O t o n i
25 2 < 1 2 < 1 >25
32 1 112 1 > 3000
Outdoor Exposure Tests
POR None
POR
POR
NBC
2246
1
1
1 1
Akron. Ohio
Los Angrles. Calif. 1 1 1. .l.o cracks. 2. Cracks risiblr .3. Cracks iiriblr w f h unaided eye.
with
CR NBC
Ozone and Weather Resistance
Accelerated ozone test data are shoivn in Table X: where the propylene oxide rubber is compared with some other rubbers. These data shoLv the POR has excellent ozone resistance when exposed under accelerated conditions. Data on outdoor weathering tests. which are generally considered to provide a more reliable index of performance, are shown in Tables XI and X I I . 'The exposures ivere made a t three different locations, which were selected to cover normal and high ozone concentrations and normal and high average temperature. T h e outdoor exposures are being continued, but it is evident that the good results obtained on accelerated tests are being substantiated. Oil and Solvent Resistance
1 8 months, bent loop specimens
Stabilizer
T h e heat resistance of propylene oxide rubber as indicated by hot air aging tests is shoivn in Table IX. 'These data show that this rubber will Lvithstand long exposures a t 250' F. with only small changes in properties. T h e elongation is still in the range of 3007, after 300 hours a t 250' F. T h e heat resistance thus appears to be substantially better than that of the highly unsaturated rubbers such as SBR and SR but a t the present stage of development is not as good as the ethylenepropylene rubbers or resin-cured butyl.
IIR None
Another feature of the propylene oxide rubber is moderate oil resistance. A comparison of CR and NBR (1 87,) is made in Table X I I I . Resistance to slvelling in aliphatic oils is good, as shown by the lo\v swell in ASTM No. 1 oil. These data indicate that this rubber will meet the general requirements for medium volume swell compounds for automotive and industrial rubber goods outlined in Class SC ASTM D 735. T h e hydrolytic stability of this rubber is also excellent and it shoivs low volume swell in water or ethylene glycol.
2 3 lo)< magn$cation. 3 3
Table XIII.
Per Cent Volume Swell (ASTM D
Table XII.
Tyj
Outdoor Exposure Tests
1 2 months,
yo retained
Fluid
properties
POR
POR
POR
CR
IIR
Stabilizer Miami. Fla.
;Tone
SBC
2246
h-BC
None
Tensile H ai dness :\kron. O h i o 'Te mile
100 103
90
90 108
94
103
90
101 104
101 103
90 104
99
105
92 104
106 99
Trnsilr
104
llardness
105
87 109
106
107 103
108 103
Hardness Los . \ n q l r s , Calif.
198
l&EC
PRODUCT
99
RESEARCH A N D
DEVELOPMENT
ASTM No 1 oil ASTM No 3011 Water
Gasoline Toluene Ethyl acetate Fuel A Fuel B Fuel C Ethylene glycol Trichloroethylene a
1460)
,a
POR
212 212 212 RT RT RT RT RT RT 212 RT
All samples exposcd for 70 hours
6 73 3 145 251 197 48 135 189 1 290
CR 9
62 10 66 160 66 16 60 105 9 165
SBR (7870)
3 36 9
60 174 126
Conclusions
Acknowledgment
This propylene oxide rubber shows levels of performance in certain properties or combinations of properties that are not available in other elastomers. Some of its prominent features are reasonably good tensile a n d tear strength, exceptional low temperature flexibility, good ozone resistance, excellent dynamic properties over a wide temperature range. good heat resistance, a n d moderate oil resistance. These properties seem important to m a n y application areas. For example, in the transportation industry this rubber would be a candidate for motor mounts, body mounts: suspension system parts, boots. hose, and tubing. I n parts around the engine that are exposed to high temperatures a n d perhaps some oil. it could outperform the conventional unsaturated elastomers. Ordnance vehicles should be able to use to good advantage the low temperature flexibility of this propylene oxide rubber, especially in parts where ozone resistance a n d oil rrsistance are also important. It is believed: therefore. that this new rubber )\-ill find its place in the ever-gro\ving family of elastomers because its properties are different in potentially useful )cays.
T h e authors thank R . A . Briggs, R.J. Herold: .4.J. Beber, and T . B. Harrison for their contributions to the synthesis of the polymer; and R.J. Emerson, LV. C. \Yarner, and H. N. Grover for assistance in the laboratory evaluation of this rubber. literature Cited (I) Bailey, F. E., Jr. (to Union Carbide Corp.), U. S. Patent 3,031,439 (April 24, 1962). (2) Bawn, C. E. H., Ledwith. A , , Quart. Rei. (London) 16, 408 (1962). ( 3 ) Furukawa, J., LMakromol.Chem. 32, 90 (1959). (4) Hendrickson, J. G., Gurgiolo, A. E.:Prescott. \V. E., 1x0 ENG.CHEM.PROD.RES.DEVELOP. 2, 199 (1963). ( 5 ) Hercules Powder Co.. Belgian Patent 579,074 (May 27, 1959). ($) Madge! E. IV.! Cheni. Ind. (London) 42, 1806 ( l 9 6 2 ) , ( / ) l a t t a , G.: .4ngeru. Chem. 6 8 , 393 (1956). (8) Price, C. C., J . Polymer Sci.34, 165 (1959). (9) Price. C. C.: Osgan, M., J . .hi. Chem. Soc. 78, 4-8' (1956). (10) Pruitt. M. E., Baggett, J. M. (to Dow Chemical C o . ) . U. S. Patent 2,706,189 (April 12. 1955). RECEIVF.D for review April 2'. 1964 ACCEPTED June 1. 1964 Division of Rubber Chemistry, Detroit: Mich., April 1964.
CATALYTIC SPECIES IN SOME ALKYL ALUMINUM TITANIUM IODIDE CATALYSTS FO R CIS- 1,4-P0 L Y BUT A D IEN E W I L L I A M
M . S A L T M A N AND T H O M A S H.
Research Dimston, The Goodyear Tire
L I N K
Rubber Co., Akron 16, Ohio
The polymerization activity of two iodine-containing coordination catalysts for formation of high cis- 1,4polybutadiene from butadiene in benzene a t 50" C. i s described. In another series of experiments, the two catalysts-Til4 plus triisobutyl aluminum and Tic14 plus iodine plus triisobutyl aluminum-were prepared, in the absence of monomer a t several AI-to-Ti mole ratios covering both active and inactive polymerization ratios, and analyzed. The reaction products o f the binary catalyst combination indicate active catalysts to include a solid, insoluble phase consisting of approximately equal parts of Tila and isobutyltitanium diiodide. A soluble component i s also required for polymerization activity, and this i s probably triisobutyl aluminum. In the ternary system, both reduction and exchange reactions occur. Active catalyst combinations contain an insoluble component which i s a mixture of reduced organotitanium chloride and iodide. Here also the triisobutyl aluminum i s the soluble cocatalyst.
many catalyst systems have been reported to be active i n the preparation of high cis-1.4-polybutadienes. the ones of major interest fall into two general classes: those \\-hich contain cobalt i n some form plus a n a l u m i n u m alkyl halide and those Lvhich contain iodine in some form plus a n a l u m i n u m alkyl. Both systems give high cis-1.4-polybutadiene although the polymers differ somewhat in cis content. molecular \\.eight distribution. a n d other properties. and perhaps even in their mechanisms of polymerization. Each catalyst really includes a ivhole family. T h e cobalt family has been more Lvidcly described in the journals (5. 6. 70). Lvhile most references to the iodine-containing systems have appeared in the patent literature ( i .7-1. 77). This paper is concerned Lvith the iodine system a n d specifically Lvith t\vo active com-
A
LTHOUGH
binations. a binary combination of a trialkyl aluminum (.AIRa) plus T i I , and a ternary combination of .AIR3 plus Tic14 plus iodine. Polymerization
Experimental Details. Triisobutyl aluminum (TIBA) and TiC1, \
